The term 'DARK PERIOD, IN ADS' can be summarized as a period of time in which advertisements were not allowed to be broadcasted. This term is often used in the context of television and radio broadcasting, and the solution to this crossword is 'NITE'. This term is an acronym for 'National Interim Television Emergency', which was a policy implemented in the United States during World War II that prohibited the broadcasting of advertisements from 8pm to 6am.